Shaped bodies of the generic type are used as refractory lining, in particular in high-temperature processes involving exposure to basic slag, e.g. in furnaces, tanks or vessels in the cement, lime, dolomite, magnesite, steel and nonferrous metals industries and also in the glass industry.
Although a shaped body composed of a resistor component (hereinafter also referred to simple as resistor) such as MgO or CaO/MgO (dolomite) has a high fire resistance and good chemical resistance, it is generally brittle because it has a relatively high modulus of elasticity (E) and an unfavorable shear modulus (G). This has an adverse effect on, in particular, the dissipation of thermal stresses, the mechanical stressability and the thermal shock resistance (TSR). It is therefore desirable to set low elastic moduli because these affect the thermomechanical durability.
To increase the elasticity or to reduce the elastic moduli, it is known that it is possible to add an elasticizer component (hereinafter also referred to simply as elasticizer) to a mix for producing a shaped body or to add raw materials which generate the elasticizer in the mix during ceramic firing.
For example, magnesia-chromite bricks or magnesia-spinel bricks which display usable shear moduli in the range from 8 to 12 GPa (gigapascal) are produced using chromium ores or synthetic spinel.
Refractory bricks containing molten hercynite or molten zirconium oxide as elasticizer have a low elasticity but are ductile. The shear moduli are from about 15 to 20 GPa and therefore relatively high.
These known elasticized, basic, refractory shaped bodies are evaluated, in particular, in respect of elasticity, desired deposit formation in a rotary tube furnace, redox resistance, alkali resistance, hydration resistance and disposability, with each of these known shaped bodies having, in terms of these properties, advantages and disadvantages, which can be seen from the following table:
TABLE 1Qualitative properties of known shaped bodiesMagnesia-Magnesia-Magnesia-Magnesia-spinelhercynitechromitezirconiaDolomitebrickbrickbrickbrickbrickElasticitygoodpoorgoodgoodpoorDepositpoorgoodgoodpoorgoodformationRedoxgoodpoorpoorgoodgoodresistanceAlkaligoodpoorpoorgoodpoorresistanceHydrationgoodgoodgoodgoodpoorresistanceDispos-goodgoodpoorgoodgoodability
Magnesia-spinel bricks and magnesia-zirconia bricks form a stable deposit in a rotary tube furnace only with difficulty; they consequently have only limited usability in, for example, the sintering zone of a rotary tube furnace for cement. Although magnesia-hercynite bricks display good deposit formation, they have a poor redox resistance and alkali resistance. The same applies to magnesia-chromite bricks which are additionally known to create disposal problems. Dolomite bricks containing no elasticizer do ensure very good deposit formation but are neither sufficiently alkali resistant nor sufficiently hydration resistant.
It is an object of the invention to provide a basic, elasticized, refractory shaped body which combines high fire resistance and good chemical resistance with, in particular, good elasticity and good deposit formation capability, and good redox, alkali and hydration resistance and can be disposed of without problems.